Line-powered instrument transformer

ABSTRACT

An instrument transformer for measuring properties of electricity in a power line is provided. The instrument transformer includes a cover section releasably secured to a base section. The cover section includes a first core segment encapsulated in a first encasement formed from a polymer resin. The base section includes a second core segment with a low voltage winding mounted thereto and a voltage transformer, all of which are encapsulated in a second encasement formed from a polymer resin. When the cover section and the base section are secured together, the first core segment adjoins the second core segment, thereby forming a current transformer having a core formed from the first and second core segments. A method for making the instrument transformer further comprises the connection of the cover section to the base section to form a passage through which a high voltage conductor may extend.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional patentapplication No. 61/345,502 filed on May 17, 2010, which is herebyincorporated by reference in its entirety.

BACKGROUND

Instrument transformers include current transformers and voltagetransformers and are used to measure the properties of electricityflowing through conductors. Current and voltage transformers are used inmeasurement and protective applications, together with equipment, suchas meters and relays. Such transformers “step down” the current and/orvoltage of a system to a standardized value that can be handled byassociated equipment. For example, a current transformer may step downcurrent in a range of 10 to 2,500 amps to a current in a range of 1 to 5amps, while a voltage transformer may step down voltage in a range of12,000 to 40,000 volts to a voltage in a range of 100 to 120 volts.Current and voltage transformers may be used to measure current andvoltage, respectively, in an elongated high voltage conductor, such asan overhead power line.

A conventional current transformer for measuring current in a highvoltage conductor typically has a unitary body with an opening throughwhich the conductor extends. Such a conventional current transformer hasa unitary core, which is circular or toroidal in shape and has a centralopening that coincides, at least partially, with the opening in thebody. With such a construction, the current transformer is mounted tothe conductor by cutting and then splicing the conductor. As can beappreciated such cutting and splicing is undesirable. Accordingly,current transformers having two-piece or split cores have been proposed.Examples of current transformers having split cores are shown in U.S.Pat. No. 4,048,605 to McCollum, U.S. Pat. No. 4,709,339 to Fernandes andUS20060279910 to Gunn et al.

The present invention is directed to an instrument transformer with animproved construction, having a split core current transformer and avoltage transformer.

SUMMARY

In accordance with the present invention, an instrument transformer formeasuring the properties of electricity flowing in an elongatedconductor is provided. The instrument transformer includes a coversection and a base section. The cover section includes a first fasteningapparatus and a first core segment having at least one end surface. Afirst encasement composed of a polymer resin encapsulates the first coresegment except for the at least one end surface. The base sectionincludes a second fastening apparatus, a second core segment having atleast one end surface, a low voltage winding disposed around the secondcore segment and a voltage transformer having a coil assembly mounted toa core. A second encasement composed of a polymer resin encapsulates thelow voltage winding, the voltage transformer and the second core segmentexcept for the at least one end surface. The first and second fasteningapparatuses engage each other to releasably secure the cover section tothe base section and to align the first and second core segments suchthat when the cover section and the base section are secured together,the at least one end surface of the first core segment adjoins the atleast one end surface of the second core segment, thereby forming acurrent transformer having a core formed from the first and second coresegments.

A method of making an instrument transformer for connection to a highvoltage conductor comprises providing a first core segment andencapsulating the first core segment with a resin to form a firstencasement. The first encasement has a generally curved first channelextending laterally through the first encasement. The method furthercomprises providing a second core segment and mounting a low voltagewinding to the second core segment. The second core segment and the lowvoltage winding are encapsulated within a resin to form a secondencasement. The second encasement has a generally curved second channelextending laterally through the second encasement. The first encasementis then attached to the second encasement using a plurality of boltsthreadably engaged with an associated one of a plurality of bore insertslocated in the first encasement. The attachment of the first encasementto the second encasement forms a passage when the first and secondchannels are joined together.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, structural embodiments are illustratedthat, together with the detailed description provided below, describeexemplary embodiments of a line-powered instrument transformer. One ofordinary skill in the art will appreciate that a component may bedesigned as multiple components or that multiple components may bedesigned as a single component.

Further, in the accompanying drawings and description that follow, likeparts are indicated throughout the drawings and written description withthe same reference numerals, respectively. The figures are not drawn toscale and the proportions of certain parts have been exaggerated forconvenience of illustration.

FIG. 1 is a front view of an instrument transformer embodied inaccordance with the present invention;

FIG. 2 is a schematic sectional view of the instrument transformer takenalong line A-A in FIG. 1;

FIG. 3 is a front view of the instrument transformer mounted to a crossbar of a utility pole, with a cover section of the instrumenttransformer spaced above a base section of the instrument transformerand with encasements of the cover and base sections shown in phantom;

FIG. 4 is a side view of the instrument transformer mounted to the crossbar of the utility pole, with the cover section of the instrumenttransformer spaced above the base section of the instrument transformerand with the encasements of the cover and base sections shown inphantom;

FIG. 5 is a schematic view of the instrument transformer and a controlbox mounted to the utility pole; and

FIG. 6 is a sectional view of a current transformer embodied inaccordance with the present invention.

DETAILED DESCRIPTION

It should be noted that in the detailed description that follows,identical components have the same reference numerals, regardless ofwhether they are shown in different embodiments of the presentinvention. It should also be noted that in order to clearly andconcisely disclose the present invention, the drawings may notnecessarily be to scale and certain features of the invention may beshown in somewhat schematic form.

As used herein, the abbreviation “CT” shall mean “current transformer”.

Referring now to FIGS. 1 and 2, there are shown views of an instrumenttransformer 10 embodied in accordance with the present invention. Theinstrument transformer 10 includes a current transformer 12 and avoltage transformer 14. One of ordinary skill in the art will recognizethat the instrument transformer 10 may be embodied as a currenttransformer 12 alone. The current transformer 12 and the voltagetransformer 14 are arranged in a cover section 18 and a base section 20that are releasably secured together. The voltage transformer 14 isfully disposed in the base section 20, while the current transformer 12is partially disposed in the cover section 18 and partially disposed inthe base section 20. The current transformer 12 is operable to measurethe current in a high voltage conductor (such as high voltage conductor38), while the voltage transformer 14 is operable to measure the voltagein the high voltage conductor 38. The voltage transformer 14 alsosupplies power to the electronics for the instrument transformer 10.

The cover section 18 includes a top or first core segment 24encapsulated in a top or first encasement 26 formed from one or morepolymer resins in a cover casting process. The first core segment 24 isgenerally U-shaped and is comprised of ferromagnetic metal, such asgrain-oriented silicon steel or amorphous steel. The first core segment24 may be formed from layers of metal strips or a stack of metal plates.An electrostatic shield 28 is disposed over and covers the first coresegment 24, except for the ends thereof. The electrostatic shield 28 maybe formed from one or more layers of semi-conductive tape that are woundover a layer of closed cell foam padding that encompasses the first coresegment 24. The first encasement 26 fully covers the first core segment24 except for the ends thereof, which are exposed at a bottom surface ofthe first encasement 26. At least a portion of the bottom surface of thefirst encasement 26 is substantially flat (planar) so as to permit thebottom surface to be disposed flush with a top surface of a secondencasement 46 of the base section 20.

A plurality of bore inserts 30 extend through the first encasement 26from the top to the bottom thereof. The bore inserts 30 are arrangedaround the first core segment 24 and are adapted to receive threadedbolts 34 for securing the cover section 18 to the base section 20, aswill be further described below. A main passage 36 extends laterallythrough the first encasement 26 and is adapted to accommodate a highvoltage conductor 38, such as an overhead power line. The high voltageconductor 38 may carry electricity at a voltage from about 1 kV to about52 kV. When the instrument transformer is installed and the high voltageconductor 38 extends through the main passage 36, a connector 40electrically connects the un-insulated high voltage conductor 38 to thefirst core segment 24 and the second core segment so that the first coresegment 24, second core segment 44, connector 40, and threaded bolts 34,are at about the same potential as the high voltage conductor 38.

The advantage of having the aforementioned components at nearly the samepotential as the un-insulated high voltage conductor 38 is thatinsulation which would otherwise be required to maintain the first andsecond core segments 24, 44 at ground potential, is not necessary.Therefore, the gap between the first and second core segments 24, 44will not be widened by the usage of insulation around the high voltageconductor 38, and the associated ends of the first and second coresegments 24, 44 will be in closer contact. The closer contact of thefirst and second core segments 24, 44, allowed by the absence ofinsulation on the high voltage conductor 38, provides increased accuracyof load current measurement. Consequently, the instrument transformer 10is able to achieve a measurement accuracy that meets metering class.

The connector 40 may be connected to a terminal 41 mounted on theoutside of the first encasement 26 and the terminal 41 may then beelectrically connected to the first core segment 24 by an internalconductor. The connector 40 may be connected to the high voltageconductor 38 by a clamp 42.

The base section 20 includes a bottom or second core segment 44encapsulated in a bottom or second encasement 46 formed from one or morepolymer resins in a base casting process. The second encasement 46 has aplurality of circumferentially-extending sheds 47. The second coresegment 44 is also generally U-shaped and has the same construction asthe first core segment 24. In one embodiment, the first and second coresegments 24, 44 are produced by constructing a single core and thencutting the core in half. The second encasement 46 fully covers thesecond core segment 44 except for the ends thereof, which are exposed ata top surface of the second encasement 46. At least a portion of the topsurface of the second encasement 46 is substantially flat (planar) so asto permit the top surface to be disposed flush with the bottom surfaceof the first encasement 26 of the cover section 12. When the coversection 12 is secured to the base section 20, the exposed ends of thefirst and second core sections 24, 44 abut each other, thereby forming(or re-forming) a core of the current transformer 12.

The second core segment 44 is supported on a cradle 48 having a C-shapedmiddle section and opposing peripheral flanges. The cradle 48 is formedfrom an epoxy resin or any material having similar properties. Mounts 50are secured to the flanges and have threaded interiors for threadablyreceiving ends of the bolts 34 extending through the bore inserts 30. Alayer of closed cell foam padding, an insulation tube 52 and a lowvoltage winding 54 are disposed over the second core segment 44 and themiddle section of the cradle 48, with the closed cell foam padding beingdisposed over the second core segment 44 and the insulation tube 52being disposed between the layer of closed cell foam padding and the lowvoltage winding 54. The insulation tube 52 is composed of a dielectricmaterial and electrically insulates the low voltage winding 54 from thesecond core segment 44. The insulation tube 52 may be comprised of adielectric resin (such as an epoxy resin), layers of an insulating tapeor a phenolic kraft paper tube (i.e., a kraft paper tube impregnatedwith a phenolic resin). The low voltage winding 54 is wound around theinsulation tube 52 and is comprised of a plurality of turns of aconductor composed of a metal, such as copper. An electrostatic shield56 is disposed over and covers the low voltage winding 54. Theelectrostatic shield 56 may be formed from one or more layers ofsemi-conductive tape that are wound over the low voltage winding 54. Thecradle 48, the insulation tube 52 and the low voltage winding 54 are allencapsulated in the second encasement 46.

The low voltage winding 54 may have a single CT ratio or multiple CTratios. In this regard, it should be noted that a CT ratio is the ratioof the rated primary current (in the high voltage conductor 38) to therated secondary current (in the low voltage winding 54). If the lowvoltage winding 54 has a multi-ratio construction, differentcombinations of taps may provide a range of CT ratios, such as from 50:5to 600:5 or from 500:5 to 4000:5. The taps are connected at differentpoints along the travel of the conductor of the low voltage winding 54.For example, if there are five taps, two of the taps may be connected atopposing ends of the low voltage winding 54 and the other three taps maybe connected to the low voltage winding 54 in between the two end tapsin a spaced apart manner. Thus, the number of turns of the low voltagewinding 54 between different pairs of taps is different, therebycreating different CT ratios. The taps on the low voltage winding 54 areconnected by conductors to terminals 57 enclosed in a junction box 58secured to the base section 20.

The voltage transformer 14 includes a winding structure 60 mounted to acore 62 comprised of ferromagnetic metal, such as grain-oriented siliconsteel or amorphous steel. As shown, the core 62 may be comprised of two,abutting rings, each of which is formed from layers of metal strips or astack of metal plates. The winding structure 60 is mounted to abuttinglegs of the rings. An insulation tube 64 is mounted to the core 62,between the core 62 and the winding structure 60. The insulation tube 64may be comprised of a dielectric resin (such as an epoxy resin), layersof an insulating tape or a phenolic kraft paper tube.

The winding structure 60 comprises a low voltage winding concentricallydisposed inside a high voltage winding. The low voltage winding and thehigh voltage winding are each comprised of a plurality of turns of aconductor composed of a metal, such as copper. Of course, the number ofturns in the two windings is different. As with the current transformer12, the core 62 and the winding structure 60 of the voltage transformer14 are each covered with an electrostatic shield, which may have thesame construction/composition as the electrostatic shields 28, 56. Thehigh voltage winding of the winding structure 60 is electricallyconnected to the high voltage conductor 38. The connection may bethrough the terminal 41 and the first core segment 24. The voltagetransformer 14 is operable to step down the voltage supplied to the highvoltage winding (e.g., about 1-35 kV) to a lower voltage at the outputof the low voltage winding. This lower voltage may be about 110-120volts, or even lower, down to a voltage of about 10 volts. The output ofthe low voltage winding is connected to the terminals 57 in the junctionbox 58. The terminals 57 include terminals for the current measurementoutput(s) from the current transformer 12 and terminals for the voltagemeasurement output from the low voltage winding of the voltagetransformer 14. The lower voltage power from the voltage transformer 14is also used to power the electronics in a control box 100 mountedseparately from the instrument transformer 10.

The cover section 18 is secured to the base section 20 by inserting thebolts 34 through the bore inserts 30 of the cover section 18 andthreadably securing the ends of the bolts 34 in the mounts 50 of thebase section 20. The bore inserts 30 in the cover section 18 and themounts of the base section 20 are positioned so as to properly align thefirst core segment 24 with the second core segment 44 to form acontiguous core for the current transformer 12 when the cover section 18and the base section 20 are secured together with the bolts 34. Thefirst encasement 26 and the second encasement 46 may also be formed withcorresponding structural features (such as ridges and grooves and holesand posts) that help properly align the cover section 18 and the basesection 20.

Referring now to FIG. 6, a current transformer 80 is depicted and hasthe same construction as the instrument transformer 10, except asdescribed below. The voltage transformer 14 included in the instrumenttransformer 10 is not part of the current transformer 80. Additionally,the current transformer 80 has two low voltage windings 77 that arearranged in a different configuration than the single low voltagewinding 54 of the instrument transformer 10. Each of the low voltagewindings 77 in the current transformer 80 are mounted to an associatedone of opposing ends of the second core segment. The low voltagewindings 77 may be connected together in series and further connected toa terminal (not shown).

Referring now to FIGS. 2 and 6, a spring mechanism 33 may be utilized toregulate the force applied to the ends of the first and second coresegments 24, 44 when the cover section 18 is secured to the base section20. The spring mechanism 33 provides the control that is required tomaintain the ends of the first and second core segmented 24, 44 in fulland even contact. The spring mechanism 33 is placed between the head ofthe threaded bolt 34 and the outer edge portion of the bore insert 30 asthe threaded bolt 34 is engaged with the bore insert 30. The springmechanism 33 may be embodied as a die spring, urethane spring, aplurality of Belleville washers, or a similar spring mechanism. When thespring mechanism 33 is embodied as a plurality of Belleville washers,the washers may be stacked in a formation having the cup end portion ofeach washer arranged opposite to the cup end portions of adjacentwashers, the cup end portions of all washers arranged in the samedirection, or a combination of the two formations. As will beappreciated by one having ordinary skill in the art, the springmechanism 33 may be used in an embodiment having only a currenttransformer 12 in addition to the instrument transformer 10 comprised ofboth a current transformer 12 and a voltage transformer 14.

The cover section 18 may be removed from the base section 20 to permitthe instrument transformer 10 to be installed to or uninstalled from thehigh voltage conductor 38, i.e., to pass the high voltage conductor 38through the current transformer 12 or remove the high voltage conductor38 from the current transformer 12. The cover section 18 is removedsimply by unthreading the bolts 34 from the mounts 50, removing thespring mechanism 33, if present, and separating the cover section 18from the base section 20.

The first and second encasements 26, 46 are formed separately in thecover casting process and the base casting process, respectively. Eachof the first and second encasements 26, 46 may be formed from a singleinsulating resin, which is an epoxy resin. In one embodiment, the resinis a cycloaliphatic epoxy resin, still more particularly a hydrophobiccycloaliphatic epoxy resin composition. Such an epoxy resin compositionmay comprise a cycloaliphatic epoxy resin, a curing agent, anaccelerator and filler, such as silanised quartz powder, fused silicapowder, or silanised fused silica powder. In one embodiment, the epoxyresin composition comprises from about 50-70% filler. The curing agentmay be an anhydride, such as a linear aliphatic polymeric anhydride, ora cyclic carboxylic anhydride. The accelerator may be an amine, anacidic catalyst (such as stannous octoate), an imidazole, or aquaternary ammonium hydroxide or halide.

The cover casting process and the base casting process may each be anautomatic pressure gelation (APG) process. In such an APG process, theresin composition (in liquid form) is degassed and preheated to atemperature above 40° C., while under vacuum. The internal components ofthe section being cast (such as the first core segment 24 and the boreinserts 30 in the cover section 18) are placed in a cavity of a moldheated to an elevated curing temperature of the resin. The degassed andpreheated resin composition is then introduced under slight pressureinto the cavity containing the internal components. Inside the cavity,the resin composition quickly starts to gel. The resin composition inthe cavity, however, remains in contact with pressurized resin beingintroduced from outside the cavity. In this manner, the shrinkage of thegelled resin composition in the cavity is compensated for by subsequentfurther addition of degassed and preheated resin composition enteringthe cavity under pressure. After the resin composition cures to a solid,the encasement with the internal components molded therein is removedfrom the mold cavity. The encasement is then allowed to fully cure.

It should be appreciated that in lieu of being formed pursuant to an APGprocess, the first and second encasements 26, 46 may be formed using anopen casting process or a vacuum casting process. In an open castingprocess, the resin composition is simply poured into an open moldcontaining the internal components and then heated to the elevatedcuring temperature of the resin. In vacuum casting, the internalcomponents are disposed in a mold enclosed in a vacuum chamber orcasing. The resin composition is mixed under vacuum and introduced intothe mold in the vacuum chamber, which is also under vacuum. The mold isheated to the elevated curing temperature of the resin. After the resincomposition is dispensed into the mold, the pressure in the vacuumchamber is raised to atmospheric pressure for curing theproto-encasement in the mold. Post curing can be performed afterdemolding the proto-encasement.

In another embodiment of the present invention, each of the first andsecond encasements 26, 46 has two layers formed from two differentinsulating resins, respectively, and is constructed in accordance withPCT Application No.: WO2008127575, which is hereby incorporated byreference. In this embodiment, the encasement comprises an inner layeror shell and an outer layer or shell. The outer shell is disposed overthe inner shell and is coextensive therewith. The inner shell is moreflexible (softer) than the outer shell, with the inner shell beingcomprised of a flexible first resin composition, while the outer shellbeing comprised of a rigid second resin composition. The first resincomposition (when fully cured) is flexible, having a tensile elongationat break (as measured by ASTM D638) of greater than 5%, moreparticularly, greater than 10%, still more particularly, greater than20%, even still more particularly, in a range from about 20% to about100%. The second resin composition (when fully cured) is rigid, having atensile elongation at break (as measured by ASTM D638) of less than 5%,more particularly, in a range from about 1% to about 5%. The first resincomposition of the inner shell may be a flexible epoxy composition, aflexible aromatic polyurethane composition, butyl rubber, or athermoplastic rubber. The second resin composition of the outer shell isa cycloaliphatic epoxy composition, such as that described above. Theencasement is formed over the internal components using first and secondcasting processes. In the first casting process, the inner shell isformed from the first resin composition in a first mold. In the secondcasting process, the intermediate product comprising the internalcomponents inside the inner shell is placed in a second mold and thenthe second resin composition is introduced into the second mold. Afterthe second resin composition (the outer shell) cures for a period oftime to form a solid, the encasement with the internal componentsdisposed therein is removed from the second mold. The outer shell isthen allowed to fully cure.

Referring now to FIGS. 3-5, the instrument transformer 10 may be mountedto a cross bar 110 of a utility pole 112 by a mounting assembly 114,which includes a mounting plate 116 secured to a bottom end of the basesection 20. The control box 100 may be mounted to the utility pole 112,below the instrument transformer 10. The control box 100 containselectronics for processing and then communicating the current andvoltage measurement values received from the current transformer 12 andthe voltage transformer 14, respectively. The electronics includes aprocessor, memory and a communication port. The electronics are operableto communicate current and voltage measurement signals through thecommunication port over a communication link to another location, whichmay be nearby, such as the base of the utility pole to which theinstrument transformer 10 and the control box 100 are mounted.Alternately and/or additionally, the current signal values may betransmitted to a remotely located control center. The communication linkmay be a physical hardwired link, a satellite link, a cellular link, amodem or telephone line link, an Internet link, a wide area or localarea network link, a wireless link and combinations of the foregoing. Inone embodiment, the communication link is a wireless link forcommunicating to a nearby location. In this embodiment, thecommunication port includes a radio transceiver connected to an antenna120 mounted to the exterior of the control box 100.

It is to be understood that the description of the foregoing exemplaryembodiment(s) is (are) intended to be only illustrative, rather thanexhaustive, of the present invention. Those of ordinary skill will beable to make certain additions, deletions, and/or modifications to theembodiment(s) of the disclosed subject matter without departing from thespirit of the invention or its scope, as defined by the appended claims.

1. An instrument transformer for measuring properties of electricityflowing in an elongated conductor, the instrument transformercomprising: (a.) a cover section comprising: a first core segment havingat least one end surface; a first encasement composed of a polymerresin, the first encasement encapsulating the first core segment exceptfor the at least one end surface; and a first fastening apparatus; (b.)a base section comprising: a second core segment having at least one endsurface; a low voltage winding disposed around the second core segment;a voltage transformer comprising a coil assembly mounted to a core; asecond encasement composed of a polymer resin, the second encasementencapsulating the low voltage winding, the voltage transformer and thesecond core segment except for the at least one end surface; and asecond fastening apparatus; and wherein the first and second fasteningapparatuses are adapted to engage each other to releasably secure thecover section to the base section and to align the first and coresegments such that when the cover section and the base section aresecured together, the at least one end surface of the first core segmentadjoins the at least one end surface of the second core segment, therebyforming a current transformer having a core formed from the first andsecond core segments.
 2. The instrument transformer of claim 1, whereinwhen the first and second fastening apparatuses are disengaged, thecover section and the base section may be separated from each other. 3.The instrument transformer of claim 2, wherein the first and secondencasements are formed in separate casting processes.
 4. The instrumenttransformer of claim 3, wherein the first and second encasements arecomprised of an epoxy resin.
 5. The instrument transformer of claim 4,wherein the epoxy resin is a cycloaliphatic epoxy resin.
 6. Theinstrument transformer of claim 2, wherein the first encasement has afirst surface through which the at least one end surface of the firstcore segment is exposed, and wherein the second encasement has a secondsurface through which the at least one end surface of the second coresegment is exposed.
 7. The instrument transformer of claim 6, wherein atleast a portion of the first surface is planar and at least a portion ofthe second surface is planar, and wherein the planar portions of thefirst and second surfaces adjoin each other when the cover section issecured to the base section.
 8. The instrument transformer of claim 1,wherein the first and second fastening apparatuses comprise bolts withthreaded ends and mounts for threadably receiving the ends of the bolts.9. The instrument transformer of claim 8, wherein the first and secondfastening apparatuses are further comprised of a spring mechanismdisposed between a head of said bolt and an outer edge portion of saidmount.
 10. The instrument transformer of claim 9, wherein the springmechanism is selected from the group consisting of a urethane spring,Belleville washers, and a die spring.
 11. A method of making aninstrument transformer for connection to a high voltage conductor,comprising: a. providing a first core segment; b. encapsulating thefirst core segment with a polymer resin to form a first encasement, saidfirst encasement having a generally arcuate first channel extendinglaterally through said first encasement; c. providing a second coresegment; d. mounting a low voltage winding to the second core segment;e. encapsulating said second core segment and said low voltage windingwithin a polymer resin to form a second encasement, said secondencasement having a generally arcuate second channel extending laterallythrough said second encasement; and f. attaching said first encasementto said second encasement using a plurality of bolts threadably engagedwith an associated one of a plurality of bore inserts, said plurality ofbore inserts located in said first encasement, the attachment of saidfirst encasement to said second encasement forming a passage from thecooperation of said first and second channels.
 12. The method of claim11 further comprising: g. placing a spring mechanism between a bolt headand a bore insert of said first encasement.
 13. The method of claim 12wherein the spring mechanism is selected from the group consisting of aurethane spring, Belleville washers and a die spring.
 14. The method ofclaim 11 further comprising: g. positioning said first encasement orsaid second encasement relative to said high voltage conductor so thatsaid high voltage conductor extends through one of said first and secondchannels and wherein the attachment of said first encasement to saidsecond encasement is performed after the positioning of said first orsaid second encasement so that said high voltage conductor extendsthrough said passage after said first and second encasements areattached.
 15. The method of claim 11 further comprising: g. providing anelectrical connection between said high voltage conductor and said firstcore segment using a connector disposed between and attached to saidhigh voltage conductor and said first core segment.